Dynamical Orbital classification of selected N-rich stars with \textit{Gaia} DR2 astrometry

Abstract

We have used the galaxy modeling algorithm \texttt{GravPot16}, to explore the more probable orbital elements of a sample of 64 selected N-rich stars across the Milky Way. Using the newly measured proper motions from \texttt{Gaia} DR2 with existing line-of-sight velocities from APOGEE-2 survey and spectrophotometric distance estimations from the \texttt{StarHorse}. We adopted a set of high-resolution particle simulations evolved in the same steady-state Galactic potential model with a bar, in order to identify the groups of N-rich stars that have a high probability of belonging to the bulge/bar, disk, and stellar halo component. We find that the vast majority of the N-rich stars show typically maximum height from the Galactic plane below 3 kpc, and develop rather eccentric orbits (\textit{e}$>$0.5), which means these stars appear to have bulge/bar-like and/or halo-like orbits. We also show that $\sim 66$\% of the selected N-rich stars currently lives in the inner Galaxy inside the corotation radius (C.R.), whilst $\sim 14$\% of the N-rich star resides in halo-like orbits. Among the N-rich in the inner Galaxy, $\sim 27\%$ of them share orbital properties in the boundary between bulge/bar and disk, depending on the bar pattern speeds. Our dynamical analysis also indicates that some of the N-rich are likely halo interlopers and therefore suggest that halo contamination is not insignificant within the bulge area.

arXiv commentResubmitted to MNRAS after minor revision, 12 pages, 3 figures, 4 Tables

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